Pin-socket connection devices with torsioned pin contacts

ABSTRACT

In this plug-in electrical connection arrangement contact pressure is established by twisting the torsionally resilient pin member of each pin-socket contact couple. The insulating base which holds and provides protective enclosures for the pin contacts also provides alignment guidance for the socket contacts. The pin contact has a torsionally resilient stem section, ideally colinear with the longitudinal axis of the socket contact, which terminates in a transversely extended contact cap section. In the process of making contact the cap is forced to rotate and torsionally flex the stem. The reaction of the stem establishes contact pressure at the lateral extremities of the cap.

United States Patent 2,882,508 4/1959 Watts 3,185,955

[72] Inventor RobertlLMcNutt 5/1965 Keller...r........

Poughkeepsie, N.Y.

7/1965 Beckwith...

n n .w w MM a H h w r mm m m m m m m 3 mm International Business Machines Corp. Armonk, N.Y.

2 ,1 ma 9" 3 ww FA a d e m mm pu AFPA 11]] 253 2247 [[[l Attorneys-Hanifin and Jancin and Robert Lieber [54] PIN-SOCKET CONNECTION DEVICES WITH ABSTRACT In this plug-in electrical connection arrange- TORSIONED PIN CONTACTS ment contact pressure is established by twisting the torsionally resilient pin member of each pin-socket contact couple. The

d provides protective enclorovides alignment guidance for insulating base which holds an sures for the pin contacts also p the socket contacts. The pin contact has a torsionally resilient stem section, ideally colinear with the longitudinal axis of the socket contact, which terminates in a transversely extended contact cap section. In the process of making contact the cap [56] References CM em The reaction UNITEDSTATESPATENTS 2,664,552 12/1953 Ericsson et is forced to rotate and torsionally flex the st of the stem establishes contact pressure at the lateral extremities of the cap.

PATENTED M1824 lsn fflllvrwllih ATTORNEY PATENIEU AUG24 |97| SHEET 2 0F 2 FIG.

FIG.

FIG. 8

PIN-SOCKET CONNECTION DEVICES WITH TORSIONED PIN CONTACTS BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to microminiature pin-socket electrical connection arrangements of the plug-in type wherein contact pressure is established through twisting flexure of a torsionally resilient pin type contact member.

2. Description of the Prior Art U.S. Pat. Nos. 2,926,328 (Flanaganland 3,333,226 (Donnelly) have representative disclosures of prior art connector arrangements in which there is torsional flexure of portions of socket-type contact elements. By referring torsional tension in the present invention to the specially constructed pin-type member I have been able to provide connections featuring desirable electrical and mechanical properties, the latter including: enhanced contact pressures, comparatively wide contact areas, greater tolerance to misalignment of contacting parts, and less effort required to initiate insertion.

SUMMARY The invention provides microminiature plug-in electrical connection devices characterized by a small initial insertion force effort, comparatively largecontact pressures, comparatively secure contact engagement at plural points of contact, and greater tolerance to misalignment of coupling elements.

Contact pressure in each pin-socket couple isestablished by twisting the conductive pin-type contact arounda filamentous torsionally resilient conductive stern section. The stems, which ideally have axes coinciding with longitudinal-shank axes of respective socket-type members,are firmlyheld at one end in an insulating base support. At the opposite'unsupported end of each stem a transverse cap projection is formed which makes the actual plug-in contact connection.

A key extension at the supported end of each stem seats securely by force-fit in a complementary aperture in the base support. The keying of this extension andparallel alignment of base apertures establishes all transverserprojections of the cap sections in a predetermined parallel orientation and transmits the torque stress placed on the contact to thecbase rather'than to external leads which may be soldered to the keyextensions. Fixedly held socket-type contacts with transverse contact channels angularly offset in relation to the contact cap sections of the pin-type contacts, within a tolerance range of angular displacement, are urged into plug-in contact with respective cap sections. Tapered surfaces of parts forming the sockettype contact channels cause capsections of respective pintype contacts to follow a helical engagement path inducing torsional stresses on respective pin-type stern sections by means of which desired contactpressures are applied to the cap sections.

The insulating base holding thepin-type contacts hascellular insulative extensions serving to electrically isolate the pin contacts and protectively enclose the fragile stemand cap formations. The cell extensions are also designed to guidethe socket-type contacts into initial engagement positions relative to respective pin caps thereby increasingthetolerance to initial misalignment of each contact couple.

The foregoing and other features, objects and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view of a contact couple according to the present invention seen in disengaged position;

FIG. 2 is a perspective view of the same contact couple shown in engagedposition with hidden parts of the engaged contact members shown in phantom;

FIG. 3 and 3a are respective side elevation and plan views of the pin-type contact member;

FIG. 4 is a perspective view of a plug-in package assembly including plural pin-type contacts in an insulative base holder and corresponding socket-type contacts held on a multilayer printed circuit board;

FIG. 5 is a sectional view of the assembly of FIG. 4 taken along lines 55 in FIG. 4, with the contacts variously shown in section and elevation, and in some positions omitted completely for demonstrative purposes;

FIG. 6 is a view partly in perspective and partly in section illustrating the key and tang extensions of the pin-type contact element and the force-fit position thereof in the complementary apertures in the insulative base;

FIGS. 7a and 7b illustrate respective front and side elevations of the stem and cap sections of one embodiment of the pin-type contact member of subject invention;

FIGS. 70 and 7d are respective front and side elevations of the stem and cap sections of a second embodiment of the pintype contact member;

FIGS. 7e and 7f are respective front and side elevations of stem and cap sections of a third embodiment of the subject contact member;

FIG. 8 is a plan view of a blank cutout from which a multiplicity of socket-type contact members can be formed;

FIG. 9 is a perspective view of a socket-type contact member formed from the cutout of FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 and 2 the subject plug-in connection arrangement features a torsionally resilient pin-type contact indicated generally at l and a complementary socket-type contact indicated generally at 2. The pin contact is distinguished by a torsionally resilient conductive stem section 3 and a conductive cap section 4 projecting transversely outward from an unsupported end 5 of the stem 3.

The socket-type contact 2 includes a conductive shank section 6 and a main conductive body section 7 formed with a pair of upraised finger sections 8, 9. The fingers form a contact channel 10, having generally U-shaped profile when viewed from the side, for receiving the cap section 4 of the pin contact in plug-in contact engagement.

Prior to engagement the remote end of the stem section 3 of the pin contact and the shank section 6 of the socket contact are gripped securely, by not shown insulative holding means described later, in a predetermined relative orientation such that the cap section 4 of the pin is skewed at an angle 12 to the direction line of the lengthwise axis of the contact channel 10. Consequently when contacts such as 1 and 2 are brought together the ends of the cap section 4 of the pin contact engage the divergently tapering side surfaces 13, 14 of the socket contact in a skewed position and are forced to rotate in the direction indicated by arrow 15. This causes the stem section of the pin contact to twist in the same direction about its longitudinal axis. Ideally the stem should be positioned with its axis coincident with'the extension of the axis of the shank 6. Tolerance to misalignment of the stem will be discussed later. As previously mentioned the stem section is torsionally resilientand therefore it reacts to the twisting deformation by setting'up an opposing internal stress which establishes the desired contact pressure of the cap section when engagement is completed.

As shown in the drawings the side surfaces of the fingers 8, 9 of the contact member 2 first taper divergently as at 13 and 14 and then drop steeply as at 16 and 17 to form the generally U- shaped side profile of contact channel 10. The inner surfaces 18 and 19 of contact 2 also have tapering sections 20 and 21, the latter hidden from view in the drawing, and steeply sloped sections 23 and 24, the latter merging to form the generally U- shaped sideprofile of channel 10.

Thus, it may now be seen that the skewed cap section 4 of contact 1 is made to follow an initially helical engagement path by the tapering side and inner surfaces of the contact fingers 8, 9 of contact 2, and then seats in the steep-sloped part of the channel without additional twisting stress as in FIG. 2. It

will be apparent that the engagement force magnitudes parallel to the axis of engagement increase gradually from the relatively low level required to enter the short and wide slot formed by the widely spaced fingertips 26, 27 of the contact 2 to the higher levels required to overcome the increasing frictional forces deriving from the torsional stress of contact 1. Obviously when engagement is completed the force on the cap section 4 reduces to only a torsional component.

It may be noted that the engaged cap section 4 makes contact at at least two points with the inner surfaces 23, 24 of contact 2, thereby muting adequacy and reliability of contact and good wiping action in each contact engagement. It is also quite apparent that the configuration of contact 2 allows for considerable tolerance in misalignment of the contacting parts. Thus, assuming that at the start of engagement the pin stem is offset to the side by some distance from the linear extension of the longitudinal axis of symmetry of the socket shank 6 the tapered inner surfaces of the socket contact compensate for the offset and direct the pin contact into the desired engagement path. As will be seen later additional stresses due to such misalignment are taken into consideration in the contact design. Similarly it may be seen that if cap section 4 is misaligned in its angular relation to the axis of longitudinal symmetry of transverse contact channel it will nonetheless, within tolerance limits, engage the contact fingets 8, 9 and follow the desired helical path of engagement. In sum the present arrangement affords considerable misalignment tolerance in stem position and cap angle.

As seen in FIGS. 3 and 3a the stem section of the pin contact terminates at the end remote from the cap section in a key extension 30 angled at a predetermined offset relative to cap 4. This angle of offset is related to the angle of offset of the cap relative to the channel 10 of the opposite contact.

In a typical package application suggested in FIG. 4, the key extensions 30 are force fitted into apertures such as 31 in an insulating base 32. This orients the respective cap sections 4 of a plurality of pin contacts at a desired torsion-producing angle relative to channels of respective contacts 2. Base 32 has insulative extensions such as 33 which form protective and isolating enclosures for the fragile and unsupported stem and cap sections of contact members 1. Extensions 33 also serve to guidecomplementary contacts such as 2 into initial engagement'positions relative to respective contacts 1 whereby a greater degree of initial misalignment between contacting parts can be tolerated.

Socket contacts 2 in the arrangement of FIG. 4 are firmly secured, through shank extensions 6 shown in FIG. 1, in corresponding apertures in a printed circuit board indicated at 34. Such a board may have multiple layers of printed circuits alternating with insulative spacing layers and may be arranged to make contact between any layer and the shank 6 of a contact member 2, in known fashion, through the aperture retaining the shank.

As may be seen in FIG. 5 the compartments formed by extensions 33 of base 32 conform rather closely to the outer shape of the body portions 7 of the contact members 2. As is further suggested in FIG. 5 the protective base 32 need not have a contact in each cell. Nor for that matter is it absolutely necessary to provide a two-dimensional grid network of cells.

If for example only one row of connections is required,

member 32 may be fashioned with a single row of cells to house a single row of pin contacts. Indeed a base may even be fashioned with a single cell to hold a single pin contact.

As suggested in FIGS. 5 and 6 the key extensions 30 of the pin contacts may be permanently connected to external conductors such as leads 35. For this purpose additional apertures 36 are provided in the base member 32 adjacent the apertures 31. The leads 35 are inserted in the apertures 36 and permanent connections to extensions 30 are efl'ected by reflowing solder carried as a precoating on extensions 30 and/or leads 35. Solder retlow is accomplished simply by application of heat to the junction of the conductors 30 and 35.

Altemately, external connections may be made directly from key extensions 30 to printed circuits placed on a surface of the insulative base member 32.

Key extensions 30 may be pulled into locked position in respective apertures 31 in base member 32 by providing an additional tang extension 38 (FIG. 6) at one end of each key extension. Such tang extensions facilitate insertion and may either be severed afterwards or retained as additional contact surfaces for soldering extema] leads such as 35.

DESIGN CONSIDERATIONS J: I 2 1rX(x)=1rd"/32 inch 0 Torque m5: full engagement is given by:

T (Na inch-lbs 7.3 10 (3.14) (10- (.1744) 3*2 W E0125 inch-lbs. Force (F,,) of Contact Pressure c T/Lc 0.0l25/0.038

0.329 lbs. E0.329(454)g. 149.5 g.

Spring Rate (K) given by: K=F,/a (in degrees) 14 .95 g./

Shear Stress= 16T(inch-lbs)/1rd(inch) E 63,700 p.s.i.

Shear Stress at cap offset of2 l 1 =1 35,000 p.s.i. Yield Point Stress calculations with additional bending stress on the contact due to an assumed lateral misalignment of 0.004 inches between stem and shank axes of coupling contacts indicate a combined tension around 114,000 p.s.i. which when combined with the 10 twist stress yields a total shear stress, due to combined bending an twisting deformation, of about 143,000 p.s.i. The empirically determined yield point for combined bend and twist deformation is around 176,000 p.s.i.

The foregoing analysis suggests that such pin contacts can easily tolerate up to 5 of angular misalignment of the cap section relative to the complementary channel and up to 0.004 inches of relative lateral misalignment between pin and socket contact centers without destruction of the pin contact or excessive diminution of contact pressure.

Tests have shown that stem center misalignments of the pin on the order of 10.006 inches in a direction perpendicular to the socket channel can be safely tolerated, and in a direction parallel to the channel even greater pin misalignments up to 0.010 inches can be tolerated.

The contacts just described exhibit insertion forces rising gradually from a small initial magnitude to a peak average magnitude of 48 grams per contact. Average extraction force is around 24 grams per contact. A peak insertion force of around 29 lbs. would be required to seat a connector plug assembly of 272 contacts. Contact pressure depends entirely on the stresses due to stem torqueing. Table 2 below shows, for example, that variations of plus or minus 2 in the cap offset angle of a contact with 0.010-inch stem diameter d produce contact pressure variations of plus or minus 30 grams from a normal value of l49.5 grams. Tables I and 2 below also indicate the dependency of pressure stress on stem diameter and length. Although not shown in the table it will be understood that pressure will also depend significantly upon the resiliency of the material used in the contact.

Electrical measurements indicate a contact DC resistance around 25Xl03 ohms for total lengths of pin and socket contacts and connecting leads up to 0.300 inches. Signal propagation delays on the order of 50 picoseconds are expected.

The torqueing stress in the pin contact is absorbed at least partly by the plastic holding member 32 and is not transmitted as a shearing stress to any solder connection joint formed between key extensions such as 30 and external leads such as 35.

Several manufacturing techniques are considered suitable for fabricating the pin contact members. As suggested in FIGS. 70 and 7b these contacts can be made by welding together separate pieces forming the stem and cap members with the not shown key extension formed as an integral extension of the stem. Laser beam welding yields especially fine joints with no outcropping of material at the juncture of stem and cap parts. Percussion welding also yields satisfactory joints which however have an outcropping of material at the weld juncture requiring provision of clearance wells such as 40 (FIG. 2) in the socket finger sections. Such wells serve to prevent undesired mechanical interference between cap and channel during engagement. The welded elements are wires formed as indicated into a substantially T-shaped configuration. Key and tang extensions are formed by pressing the stem end while the latter is in a soft or annealed condition, and then hardening to establish the desired material strength.

As suggested in FIGS. 7c and 7d the contact may be made from a single blank of material into a generally T-shaped configuration. This unitary structure maybe formed by etching or chemically milling a starting blank or by application to the blank of a high resolution punching technique known in the trade as Fine Flow Pressing. The latter method has shown a capability of producing parts having a width dimension no greater than stock thickness. Chemical milling followed by electropolishing produces uniformly rounded cap edges which should not interfere with or scratch channel surfaces. The key and tang extensions are produced by twisting the annealed stem end.

The generally deltoid cap configuration suggested in FIGS. 7e and 7f may be produced by bending and hardening one end of the annealed part forming the stem and cap.

Socket-type contact elements may be produced from sheet metal stock in a mass punching, stamping or etching operation suggested by the parts shown in FIGS. 8 and 9.

We have shown and described above the fundamental novel features of the invention as applied to several preferred embodiments. It will be understood that various omissions, substitutions and changes in form and detail of the invention as described herein may be made by those skilled in the art without departing from the true spirit and scope of the inventron.

It is the intention therefore to be limited only by the scope of the following claims. What is claimed is:

1. In a microminiature socket-type connector assembly including:

insulative holding means having an orifice and electrically conductive socket-type contact means having a shank section adapted to fit securely in said orifice in a force fit, the improvement in said contact means of:

a pair of relatively wide contact finger sections projecting outward from said shank section in a direction parallel to the shank axis and forming therewith an engagement channel;

said finger sections having spaced-apart convergently tapering facing surfaces near the outer tip extremities adapted to receive in twisting engagement a conductor disposed at an angle to said channel;

said facing surfaces dropping steeply at the end of said convergent taper and joining together near said shank to complete the contact-seating portion of said channel, said channel extending perpendicular to the shank and having said contact-seating portion thereof generally U-shaped in sectional appearance, said channel adapted to hold a length of a said conductor in intimate torsioned contact engagement in said U-shaped portion so that a positive external force is required to dislodge the conductor;

said finger sections being additionally distinguished by side surfaces which taper divergently from said tip extremities in the direction of said shank.

2. In a microminiature socket-type connector assembly including:

insulative holding means having an orifice and electrically conductive socket-type contact means having a shank section adapted to fit securely in said orifice in a force fit, the improvement in said contact means of:

a pair of relatively wide contact finger sections projecting outward from said shank section in a direction parallel to the shank axis and forming therewith an engagement channel;

said finger sections having spaced-apart convergently tapering facing surfaces near the outer tip extremities adapted to receive in twisting engagement a conductor disposed at an angle to said channel;

said facing surfaces dropping steeply at the end of said convergent taper and joining together near said shank to complete the contact-seating portion of said channel, said channel extending perpendicular to the shank and having said contact-seating portion thereof generally U-shaped in sectional appearance, said channel adapted to hold a length of a said conductor in intimate torsioned contact engagement in said U-shaped portion so that a positive external force is required to dislodge the conductor;

said socket-type contact means being adapted for plug-in engagement with twistable pin-type contacts held by holding means having protective cellular insulative extensions surrounding the contact-making portions of said pins, said finger sections being distinguished further by side surfaces, which taper divergently downward from said tips towards said shank and rounded back surfaces;

said side and back surfaces serving to cooperate with the cellular insulative extensions-of said pin contact holding means to guide the said socket-type contact means into a desired initial engagement attitude relative to a respective said pin-type contact;

said side surfaces serving also to define a helical engagement path for said respective pin-type contact as it enters said channel and thereby torsionally flex said pin-type contact in order to establish a desired contact pressure.

3. An electrical connector assembly comprising:

a plurality of subminiature electrically conductive pin and socket terminal members adapted for paired ganged relatively twisting engagement, said pin members having filamentary torsionable construction; and

an insulative base member retaining said pin members, said base member having compartmentalized projections, forming engagement-guiding channels for said socket members and providing electrical and physical protective isolation for the pin members;

said pin terminal members comprising:

a first thin elongated conductive stem portion adapted at one end thereof to be securely attached to said base member and having throughout the length thereof a high yield point for twist and bend stressing; and

a second thin conductive contact-making portion connected to the free end of said stem portion to form with said stem portion a T-shaped contact terminal subject to twisting engagement with a said socket member;

each said pin member containing an outcropping weld juncture connecting said stem and contact-making portions and a matching socket member containing a clearance well to provide engagement clearance for said outcropping whereby said outcropping does not impede engagement of said matching pin and socket members.

4. An electrical connector assembly comprising;

a plurality of subminiature electrically conductive pin and socket terminal members adapted for paired ganged relatively twisting engagement, said pin members having filamentary torsionable construction; and

an insulative base member retaining said pin members, said base member having compartmentalized projections, forming engagement-guiding channels for said socket members and providing electrical and physical protective isolation for the pin members;

said pin terminal members comprising:

a first thin elongated conductive stem portion adapted at one end thereof to be securely attached to said base member and having throughout the length thereof a high yield point for twist and bend stressing; and

a second thin conductive contact-making portion connected to the free end of said stem portion to form with said stem portion a T-shaped contact terminal subject to twisting engagement with a said socket member;

each said pin member having a said contact-making portion formed as a deltoid-bent, integral extensionof said stem portion.

5. An electrical connector assembly comprising:

a plurality of subminiature electrically conductive pin and socket terminal members adapted for paired ganged relatively twisting engagement, said pin members having filamentary torsionable construction; and

an insulative base member retaining said pin members, said base member having compartmentalized projections, forming engagement-guiding channels for said socket members and providing electrical and physical protective isolation for the pin members;

said pin terminal members comprising:

a first thin elongated conductive stem portion adapted at one end thereof to be securely attached to said base member and having throughout the length thereof a high yield point for twist and bend stressing; and

a second thin conductive contact-making portion connected to the free end of said stem portion to form with said stem portion a T-shaped contact terminal subject to twisting engagement with a said socket member;

each said socket terminal member adapted to engage and twist said T-shaped contact terminal formed by said pin member, said socket member having a tapered extremity for easing said contact-making portion of said pm member into a rotationally stressed engagement position as contact engagement is initiated, and an untapered contact-seating portion for securing said contact-making pin portion in final engagement position while removing therefrom the engagement-opposing component of the forces exerted by the tapered extremity. 

1. In a microminiature socket-type connector assembly including: insulative holding means having an orifice and electrically conductive socket-type contact means having a shank section adapted to fit securely in said orifice in a force fit, the improvement in said contact means of: a pair of relatively wide contact finger sections projecting outward from said shank section in a direction parallel to the shank axis and forming therewith an engagement channel; said finger sections having spaced-apart convergently tapering facing surfaces near the outer tip extremities adapted to receive in twisting engagement a conductor disposed at an angle to said channel; said facing surfaces dropping steeply at the end of said convergent taper and joining together near said shank to complete the contact-seating portion of said channel, said channel extending perpendicular to the shank and having said contact-seating portion thereof generally U-shaped in sectional appearance, said channel adapted to hold a length of a said conductor in intimate torsioned contact engagement in said Ushaped portion so that a positive external force is required to dislodge the conductor; said finger sections being additionally distinguished by side surfaces which taper divergently from said tip extremities in the direction of said shank.
 2. In a microminiature socket-type connector assembly including: insulative holding means having an orifice and electrically conductive socket-type contact means having a shank section adapted to fit securely in said orifice in a force fit, the improvement in said contact means of: a pair of relatively wide contact finger sections projecting outward from said shank section in a direction parallel to the shank axis and forming therewith an engagement channel; said finger sections having spaced-apart convergently tapering facing surfaces near the outer tip extremities adapted to receive in twisting engagement a conductor disposed at an angle to said channel; said facing surfaces dropping steeply at the end of said convergent taper and joining together near said shank to complete the contact-seating portion of said channel, said channel extending perpendicular to the shank and having said contact-seating portion thereof generally U-shaped in sectional apPearance, said channel adapted to hold a length of a said conductor in intimate torsioned contact engagement in said U-shaped portion so that a positive external force is required to dislodge the conductor; said socket-type contact means being adapted for plug-in engagement with twistable pin-type contacts held by holding means having protective cellular insulative extensions surrounding the contact-making portions of said pins, said finger sections being distinguished further by side surfaces, which taper divergently downward from said tips towards said shank and rounded back surfaces; said side and back surfaces serving to cooperate with the cellular insulative extensions of said pin contact holding means to guide the said socket-type contact means into a desired initial engagement attitude relative to a respective said pin-type contact; said side surfaces serving also to define a helical engagement path for said respective pin-type contact as it enters said channel and thereby torsionally flex said pin-type contact in order to establish a desired contact pressure.
 3. An electrical connector assembly comprising: a plurality of subminiature electrically conductive pin and socket terminal members adapted for paired ganged relatively twisting engagement, said pin members having filamentary torsionable construction; and an insulative base member retaining said pin members, said base member having compartmentalized projections, forming engagement-guiding channels for said socket members and providing electrical and physical protective isolation for the pin members; said pin terminal members comprising: a first thin elongated conductive stem portion adapted at one end thereof to be securely attached to said base member and having throughout the length thereof a high yield point for twist and bend stressing; and a second thin conductive contact-making portion connected to the free end of said stem portion to form with said stem portion a T-shaped contact terminal subject to twisting engagement with a said socket member; each said pin member containing an outcropping weld juncture connecting said stem and contact-making portions and a matching socket member containing a clearance well to provide engagement clearance for said outcropping whereby said outcropping does not impede engagement of said matching pin and socket members.
 4. An electrical connector assembly comprising; a plurality of subminiature electrically conductive pin and socket terminal members adapted for paired ganged relatively twisting engagement, said pin members having filamentary torsionable construction; and an insulative base member retaining said pin members, said base member having compartmentalized projections, forming engagement-guiding channels for said socket members and providing electrical and physical protective isolation for the pin members; said pin terminal members comprising: a first thin elongated conductive stem portion adapted at one end thereof to be securely attached to said base member and having throughout the length thereof a high yield point for twist and bend stressing; and a second thin conductive contact-making portion connected to the free end of said stem portion to form with said stem portion a T-shaped contact terminal subject to twisting engagement with a said socket member; each said pin member having a said contact-making portion formed as a deltoid-bent, integral extension of said stem portion.
 5. An electrical connector assembly comprising: a plurality of subminiature electrically conductive pin and socket terminal members adapted for paired ganged relatively twisting engagement, said pin members having filamentary torsionable construction; and an insulative base member retaining said pin members, said base member having compartmentalized projections, forming engagement-guiding channels for said socket members and providing electrical and physical protective isolation foR the pin members; said pin terminal members comprising: a first thin elongated conductive stem portion adapted at one end thereof to be securely attached to said base member and having throughout the length thereof a high yield point for twist and bend stressing; and a second thin conductive contact-making portion connected to the free end of said stem portion to form with said stem portion a T-shaped contact terminal subject to twisting engagement with a said socket member; each said socket terminal member adapted to engage and twist said T-shaped contact terminal formed by said pin member, said socket member having a tapered extremity for easing said contact-making portion of said pin member into a rotationally stressed engagement position as contact engagement is initiated, and an untapered contact-seating portion for securing said contact-making pin portion in final engagement position while removing therefrom the engagement-opposing component of the forces exerted by the tapered extremity. 